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Abstract/Description

Save fuelwood and increase control over temperature

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Solar-powered fans for tobacco curing
Cue:
Using solar panels to generate electricity is not a new technology, but there are still relatively few examples of it being used in Africa. Major drawbacks include the cost of installing solar systems and also problems with theft.
But in Malawi, a project working with tobacco farmers is proving that solar-generated electricity can play a useful part in agricultural production. The project is focusing on the curing of tobacco; this is the process by which green tobacco leaves are carefully dried under controlled conditions, in order to preserve the aroma and the valued chemicals in the leaves, ready for sale and manufacturing into cigarettes.
Curing of tobacco often requires large quantities of firewood, and has been blamed for deforestation. So could the solar-powered process be a more environmentally friendly method?
To find out how the system works, Excello Zidana went to the Ministry of Energy and Mining to meet Chief Energy Officer, Lewis Mhango. Mr Mhango began by explaining how the tobacco curing process works.
IN: ?The normal way of curing tobacco ?
OUT: ? the properties of those fruits.?
DUR?N: 5?01?
BACK ANNOUNCEMENT: The interview comes from a resource pack produced by CTA.
Transcript
Mhango The normal way of curing tobacco, especially flue-cured tobacco, is they dig a hole in the wall and then they stock firewood in a fire chamber, and then the normal flow of air takes the flues into the flue pipes, and then the heat is emitted in the room and then the tobacco gets cured. But the use of solar fans has revolutionised the process of curing tobacco, especially for smallholder farmers. Because what it does is that you have a solar panel, and then that solar panel is connected to a battery, and then the power is preserved in the battery during the day. And then at night you plug in, it is connected to a solar fan, which is a DC fan. So this fan is put at the fire chamber. So the fan drives the flues into the flue pipes from the fire chamber. Now that forced draught into the flue pipes, you can control the temperature very easily, one. Two, you can dry the tobacco very fast, since you are able to control the temperature it means you reach the required temperatures very easily, and then you control at that particular time, so the tobacco that maybe takes one week to cure, you can do it in three days. So the time is also reduced, and then the amount of firewood is also reduced. The savings are phenomenal, that?s why farmers have liked the solar fans. So the process is a combination of a solar powered fan and a little firewood.
Zidana So in the process, the function of the fan is to regulate the heat?
Mhango Yes, definitely. To regulate the heat, and to regulate the heat in such a way that if you want higher heat quicker, you can attain it very fast with a solar fan. While if you use the natural flow, it means you have to keep on stocking and stocking the firewood and then your heap is finishing, you need more firewood. But with this one, with the little firewood that you have, you force the draught quickly, the draught is going out in there, in the process the solar fan is also keeping the fire always burning, so that you generate the heat faster.
Zidana Is there any difference in quality of tobacco between the two systems, the one that uses the solar powered energy and the other one that uses maybe the fuel without the solar powered energy?
Mhango Yes, the difference is quite phenomenal. The target is to get a gold leaf, which is favoured on the auction floors. So with a solar powered fan, because you are able to control the temperatures, then you can maintain the temperatures for sometime, and then the colouring, the gold colouring, you can even monitor using a thermometer in terms of the temperature. So you attain the required temperature very easily using the solar fan.
Zidana And what are the probable advantages or disadvantages of this system?
Mhango The major advantage is, as I say, it reduces your cost of curing the tobacco, one. Two, the amount of firewood people are using is reduced, therefore you are also reducing deforestation. The third advantage is that the quality of leaf is excellent, and then the farmer fetches higher amounts of money at the auction floors, because he is able to produce good quality tobacco. But there are also some disadvantages. The major disadvantage is the initial cost of solar is quite high, although if the farmer plans properly he can still recover the cost within a short period of time, because the quality of the tobacco will fetch higher amounts of money, and therefore he can recover his money quickly. And again, if you have solar, when you are through with your tobacco curing, the solar you can also connect to lights in your house, you can also play your radio, you can also have your TV.
Zidana So you kill several birds with one stone?
Mhango With one stone.
Zidana Now, does this system need to be for large-scale curing or drying, or would it be possible to have a smaller scale version of the technology?
Mhango Yes, when we started the project we were trying to look at the possibility of having large farms to use the solar, because of the cost. But we did discover that the amount of tobacco that goes through large farms is quite huge, that the solar fan would not be ideal for large farms. So we are targeting smallholder farmers. These are the farmers who produce between 5,000 and 10,000 kg of tobacco a year.
Zidana And what other crops might this kind of system be relevant for?
Mhango It could be relevant for preserving vegetables, and probably there is also the possibility of maybe preserving fruits, but for fruit preservation we need a bit more research to make sure that it will not denature the properties of those fruits. End of track